In a commonly assigned, earlier filed, copending application of the present inventors Ser. No. 721,728 a novel and improved carburetion system for an automotive engine is shown to comprise a carburetor having an air-fuel passage, an air-inlet to the passage, a fuel inlet to the passage for mixing fuel and air in the passage, and an outlet from the passage for delivering a mixture of air and vaporized fuel to the engine. In that improved carburetion system, a heater means comprising a body of ceramic resistor material of positive temperature coefficient of resistivity is provided with a plurality of passages extending through the resistor body and with means for directing electrical current through the body to heat the body. The heater means is mounted at the outlet of the carburetor air-fuel passage for passing the air-fuel mixture through the heater passages in heat transfer relation to the body, thereby to facilitate vaporization of the fuel prior to delivery of the air-fuel mixture to the engine. The heater means is adapted to be engergized upon initiation of engine operation. In this way, the improved carburetion system of the noted earlier application is adapted to enhance fuel efficiency during engine start up and, particularly, where engine start up occurs in low ambient temperature conditions, is adapted to reduce the emission of unburned hydrocarbon pollutants and the like to the atmosphere in the engine exhaust.
However, it has been found that it is difficult to achieve efficient operation of the heater means in such a system from a 12 volt automotive power supply, that improved heater efficiency is of particular importance in order to achieve a desired degree of improvement in fuel vaporization utilizing the available power, and that it is desirable to achieve this improved degree of fuel vaporization without imposing excessive restriction on flow of the air-fuel mixture to the engine.
It is an object of this invention to provide a novel and improved high efficiency early fuel evaporation carburetion system for an automobile engine; to provide such an improved system which is operable without unduly restricting the flow of an air-fuel mixture to the engine; to provide such an improved system which is efficiently operable from a 12 volt automotive power supply; to provide such an improved system which is adapted to achieve improved fuel efficiency and reduction in exhaust gas pollutants in initiating engine operation from a cold start; and to provide such an improved system which is of simple, compact, rugged and inexpensive structure.
Briefly described, the novel and improved carburetion system of this invention includes a conventional carburetor having an air-fuel passage, an air inlet to the passage, a fuel inlet to the passage for mixing fuel with air in the air-fuel passage, and an outlet from the air-fuel passage for delivering a mixture of air and vaporized fuel to an automotive engine. A heater means comprising a body of ceramic material of positive temperature coefficient of resistivity having a plurality of passages extending through the body has means for directing electrical current through the body and is mounted at the outlet of the carburetor air-fuel passage for passing the air-fuel mixture through the heater passages in heat-transfer relation to the heater body. In accordance with this invention, the heater body is provided with a relatively small number of passages of relatively large cross sectional size for defining very thin webs of the resistor material between the passages so that the air-fuel mixture is passed readily through the heater passages without unduly impeding the flow of the air-fuel mixture to the engine. Ohmic contacts are disposed on the resistor body along the inner walls of the resistor body passages for providing the resistor body with a large effective ohmic contact area to the resistor body material. The ohmic contacts formed on the walls of alternate body passages are electrically connected together at one end of the body, preferably by a first coating of electrically conductive material which is formed on that one body end and which also extends around the side of the body adjacent that one body end. The ohmic contacts in the other body passages are electrically connected together at the opposite end of the body by a second coating of electrically conductive material on that opposite body end which also extends around the sides of the body adjacent that opposite body end. The resistor body is mounted within a housing of rigid electrically insulating material which has apertures on the opposite sides thereof aligned with the heater passages. The housing also includes mounting holes and the like for mounting the heater between the carburetor and the intake manifold of the automotive engine. A pair of generally wave-shaped annular terminals are mounted within the housing extending around the resistor body in resilient engagement with the first and second coatings respectively at the sides of the resistor body, each of the terminals having a portion extending exteriorly of the housing to be connected in the 12 volt power supply of the automobile. The heater means is preferably arranged to be energized when operation of the engine is initiated and to be effectively deenergized thereafter when the engine has warmed up to its optimum operating temperature.
In this arrangement, the carburetion system does not unduly restrict the flow of air-fuel mixture to the engine. However, the 12 volt power supply of the automobile is effective to direct a substantial electrical current through the thin webs of the resistor body material between ohmic contacts of different polarity formed within adjacent body passages. In this way, the heater means of the system efficiently generates a large amount of heat with the available power for heating the air-fuel mixture passing through the heater passages to provide significantly improved vaporization of the fuel in the mixture. Further, the heater means used in the system is compact, rugged and inexpensive and is easily utilized with a conventional carburetor without excessively increasing the height of the system over the automobile engine.